Muting systems for radio frequency (RF) receivers are known. Such systems have been used to suppress noise at an output of a radio receiver. In older radios muting systems were used to suppress noise at the output of the radio by disabling the audio output of a received signal in the absence of a desired signal. In such cases muting is activated by comparison of a received signal with a threshold value. If the received signal does not exceed the threshold then the signal was deemed absent and the radio muted. Where a competing signal stronger than the desired signal was present, on the other hand, the muting system fails.
Muting systems in radios, in the past, have been provided to improve the quality of audio signals perceived by an operator. Such muting systems accomplished such objective by completely suppressing the received signal or simply reducing the output level of the signal.
Digital error detection systems are also known. Error detection systems are pervasively used where digital signals are exchanged. Such detection systems typically include a parity bit or some other indication of the accuracy of the information within a transmitted digital word.
In the context of contemporary digital radio communication systems, audio signals are typically converted into digital representations of the audio signal and transmitted within frames containing error correction/detection coding. A digital receiver within the system, upon receipt of a frame of information, compares the received information with the error coding as a measure of the accuracy of the received data word. If the error coding indicates that the data is erroneous the receiver simply discards the erroneous data.
The suppression of erroneous data in digital receivers has largely replaced the muting function of earlier radios. Since only erroneous data is discarded an intelligible signal may be recovered even under conditions of weak signal reception.
While error detection systems have considerably improved the performance of radio receivers over prior art analog systems, problems are still experienced under conditions of very weak signal reception or where a significant portion of the data is corrupted. Where significant errors exist within a received signal, a large percentage of the signal may be discarded. Without the missing data the received signal may have audio gaps producing a choppy audio effect that may, or may not, be intelligible.
Prior art muting systems were typically provided with an fixed attenuation level depending on a signal threshold. With the adjustable threshold, a very weak signal including considerable interference may still be discernable by an operator. Digital systems that delete erroneous data do not have the capability of allowing partially corrupted data to be monitored by an operator. Because of the importance of communication systems a need exists for a method of including at least a portion of corrupted data within a recovered signal.